JAC was supported by a NERC Postdoctoral Fellowship (NE/J018325/1); SB and JAC acknowledge funding from the Danish National Research Foundation (DNRF53); SB was supported by the Swedish Research Council (grants 2010-3929 and 2013-4290); KV was supported by funding from Science without Borders (Brazil); PCJD was supported by a Royal Society Wolfson Merit Award, a Leverhulme Trust Research Fellowship and Natural Environment Research Council standard grant NE/F00348X/1. We also acknowledge support from EU FP7 grant agreement 312284 (CALIPSO), and the Paul Scherrer Institute Projects 20100167, 20110963, 20130185, 20141047.